1. Field of the Invention
The present invention relates to electrical connectors for power cords and the like. More particularly, the present invention relates to rotatable connectors comprised of self-locking male and female components.
2. Description of the Prior Art
Electrical power cords are used in many different applications to conduct electricity from a power source to an electrically powered apparatus. Power cords are used in connection with all types of electronic equipment such as stereos, computers, portable electric appliances such as those typically found in a kitchen, hand-held power tools and the like. Power cords can be formed having virtually any length, from one foot or less to hundreds of feet. Those longer cords, often referred to as extension cords, allow an apparatus connected to the cord to be more portable, as the use of the device will not be restricted by or limited to the location of the power source. Thus, it will be appreciated that power cords serve a number of useful functions in connection with many different types of devices.
One significant drawback associated with power cords is that such cords often tend to twist or become knotted during use. This problem is especially prevalent in connection with equipment that is continuously moved around relative to the power source, such as typical hand-held power tools. A tangled or twisted cord results in a reduction of the effective length of the power cord, which limits the useful range of the tool coupled to the power cord. This requires that the user manually untangle the cord, which is inconvenient, annoying, and time-consuming.
In addition, continual twisting or knotting of a cord can cause stress or strain on the cord. The conductors housed inside the cord may become crimped or may even break, resulting in a shortened useful life of the power cord.
A number of swivel connector designs have been proposed by others in an attempt to overcome the above-described disadvantages. One of those prior art devices includes a plurality of bearings and interposed insulating washers in a housing. A form of that device is disclosed in U.S. Pat. No. 1,649,276 to Adam. The bearings include inner and outer races connected to electric leads from a pair of severed power cord segments. The ends of the electric leads are sandwiched between the inner races and the adjacent insulating washers to effect an electrical connection with the inner races. It will be appreciated that any relative displacement of the bearings and washers will likely create a short circuit, as the electric leads are not securely connected to those races.
Another rotatable, multiple lead connector found in the prior art includes a receptacle with a conically shaped internal bore to receive a generally frusto-conically shaped plug. A form of this device is disclosed in U.S. Pat. No. 3,193,636 to Daniels. The receptacle includes a plurality of radially inwardly projecting V-shaped conductive contacts at axially and circumferentially spaced apart locations. Outwardly projecting, conductive contact rings with V-shaped grooves are formed on the periphery of the plug to engage the contacts and make electrical contact while allowing the plug to be rotated relative to the receptacle as the V-shaped tips ride in the V-shaped grooves. Such a device requires a rather elaborate and detailed construction.
Yet another prior art swivel device includes male and female connectors formed with complementary concave and convex circumferential regions to establish electrical contact and to provide for relative rotation. A form of this device is disclosed in U.S. Pat. No. 5,409,403 to Falossi et. al. The concave and convex sections are conductive and electrically connected to electric wires from a pair of power cord segments. Use of this device results in relative rotation between the electrical contacts which over time may cause a wearing down of the contact surfaces and thus an open circuit.
Therefore, it appears that there continues to be a need for a rotatable electrical connector which is relatively simple to construct and which provides dependable electrical connections while permitting free rotation. The present invention addresses these needs.
Inadvertent removal of an electrical plug from a socket or other receptacle that supplies electrical power has been a matter of concern since electrical appliances became common. Almost everyone who has ever used a hand mixer, vacuum cleaner, power tool, or other hand-manipulated electrical appliance has accidentally pulled the plug out of its interactive receptacle. At best, such interruptions are annoying and inconvenient for the user, who has to stop work to re-insert the plug before he can continue. In some situations, replacing the plug significantly disrupts work in progress, as when a construction worker has to climb down a ladder to replace the plug, then climb back up to resume work. Over time, repeated stress on the plug may damage the conductors to the point that the power cord must be replaced. In some situations, damaged plugs and loose connections can lead to potentially dangerous sparking and electrical shorts.
A wide variety of locking electrical adapters and connectors, for wall outlets, plugs, sockets, extension cords and the like, have been developed in response to these concerns. Many of these devices have slidable actuators and/or locking blocks for securing the prongs of an electrical plug into a wall outlet. Burkhart, Sr. provides such a device, which has a lockable, spring-loaded socket with a pair of hinged jaws for retaining an electrical plug in place (U.S. Pat. No. 5,551,884). The plug can be released from the socket by simply pushing it inwards, then allowing it to be thrust out under spring pressure.
In U.S. Pat. No. 5,108,301, Torok discloses a locking cord connector that includes a non-conductive housing, a pair of conductors each having a male and female electrical contact (each with leaf-type springs), two spring-loaded locking mechanisms with slide blocks, and a slidable actuator. The first locking mechanism locks the male electrical contacts to a receptacle; the second locks the female contacts to another plug (such as a conventional plug of an electrical appliance). Long shows a socket with a releasable locking mechanism (U.S. Pat. No. 4,909,749). His device includes a housing that contains transversely spaced contact bars and a cam-operated clamp that locks the contact bars and the prongs of a plug together to deter removal.
Borges discloses a self-locking electrical connector consisting of a male plug and a female receptacle (U.S. Pat. No. 4,867,697). The receptacle includes a self-locking mechanism with a spring-loaded locking block which automatically locks the two parts together after insertion of the prongs of the male plug.
Strand's connector, described in U.S. Pat. No. 4,700,997, is designed for attaching a flat electrode (such as an EEG electrode) to a cable. The connector includes resilient upper and lower jaws that are joined at their respective rear ends by a flexible, resilient spring, and a slidable actuator that compresses the jaws together to hold a flat electrode in place.
Hong's device (U.S. Pat. No. 4,627,681) includes a movable wedge for pressing the male and female contacts together, whereas Imhoff's plug (U.S. Pat. No. 4,544,216) has a locking ground prong with a longitudinal “V”-shaped or “U”-shaped recess that holds a slidable, spring-loaded locking member. Warner, et. al. provide a locking electric receptacle that includes a push-button rod and toggle mechanism for frictionally engaging the prongs of a male plug (U.S. Pat. No. 3,710,304).
Mangold (U.S. Pat. No. 2,435,586) and Cornwell (U.S. Pat. No. 2,261,615) provide plugs that can be laterally expanded upon insertion into a socket in order to maintain good electrical contact. Both devices include slide actuators for moving the elements that expand the prongs. Osborn's connector has a coupler with two notched tongues, teeth shaped to engage the tongues, and a transverse slidable actuator for locking it into position (U.S. Pat. No. 1,536,688).
Torok (U.S. Pat. No. 5,197,897) discloses a mechanism which is self-locking and also rotatable. His device has a non-conductive housing, a pair of conductors, two spring-loaded locking mechanisms with slide blocks, and a slidable actuator. One of the locking mechanisms locks the male electrical contacts to a receptacle; the other locks the female contacts to another plug.
Other designs include Garrison's three-prong plug with a hollow, locking ground prong (U.S. Pat. No. 5,480,318). A spring-loaded catch that engages the front wall of a socket or wall outlet is attached to the prong. The catch can be released by pushing the spring in with a nonconducting rod. Dynia's locking connector (U.S. Pat. No. 5,427,543) includes two “U”-shaped connectors for receiving the prongs of an electrical plug. A sliding cam assembly activates a spring-loaded pin to compress the sides of the connectors and retain the prongs in place. Ursich provides a self-locking female electrical socket with an automatic release mechanism and two balls that engage the holes in the prongs to secure them in place (U.S. Pat. Nos. 5,393,239 and 5,129,836). The actuator consists of a shaft with a cut-out area that permits the user to engage/disengage the balls mounted in the body of the device.
Notwithstanding the wide variety of designs encompassed by the prior art, many presently-available locking connectors and adapters are relatively complex, correspondingly difficult and expensive to manufacture, and too delicate and breakage-prone for long-term household or industrial use. Some locking connectors require special tools to disengage and remove a locked plug, and many cannot accommodate a third, ground wire conductor or polarized prongs of the male component.
There is a continuing need for locking electrical adapters and connectors which can be used to releasably secure a plug to a conventional extension cord socket, or the like. Such devices should be simple and easy to manufacture, easy to use, and enhance the safe and uninterrupted use of electrical appliances and tools that frequently require the dragging or hanging of portions of the power cord (or extension cord) during use.
It is accordingly an object of the present invention to provide a coupling for electrical cables, said coupling comprised of male and female components that are self-locking and permit rotation axially with respect to said cables.
It is another object of this invention to provide a coupling as in the foregoing objective wherein said cables include two power conductors and a third, ground conductor line, and said coupling automatically achieves continuity of all three of said lines.
It is a further object of the present invention to provide a coupling of the aforesaid nature wherein said two power conductor lines are polarized, and said coupling automatically preserves the polarity of the interconnected power conductor lines.
It is a still further object of this invention to provide a coupling of the aforesaid nature of simple, rugged design amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.